In modern digital communications systems, advanced transmission techniques are being implemented to increase link capacity and spectral efficiency. Many of these methods utilize multiple antennas to transmit and receive signals. Examples of multi-antenna systems included beamforming, MIMO, and Spatial Division Multiplexing (SDMA). As an example, in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE), Orthogonal Frequency Division Multiplexing (OFDM) is adopted as a downlink (DL) transmission scheme, and all of the referenced multi-antenna methods are potentially utilized.